As Obama slashes funding for the U.S. hydrogen fuel cell program, hydrogen enthusiasts are going open source. Autocar reports that U.K.-based personal transport maker Riversimple will unveil its Smart car-sized hydrogen-powered vehicle on June 16. The vehicle’s size, fuel efficiency and other vital statistics have already been posted on the Hyrban wiki Web site.

For the last three years, Sebastian Piech and other members of the Porsche family have been bankrolling the development of the Riversimple Urban Car in conjunction with Oxford University and Cranfield University.

What have they accomplished?  The Urban Car weighs just 772 pounds (350 kilograms), can reach speeds of 50 miles (81 kilometers) per hour, and has a range of more than 200 miles (322 kilometers). It runs off a tiny six kilowatt fuel cell, far smaller than the 100 kilowatt system found in the Honda Clarity.  Four electric motors, one on each wheel, also function as the brakes and electricity generators.*

“The Riversimple Urban Car represents a major step towards practical 21st century personal transport and towards the fulfillment of my great-grandfather’s ambitions for accessible personal transport but this time combining his other passions: light weight and high efficiency," Piech told Autocar.

The company plans to roll out 10 prototypes initially and then set up a pilot program with a city in the United Kingdom.  The cars will be leased over 20 years, with fuel included in the cost.

Of course, if that doesn’t sound good to you, you can always make your own.  The engineers will soon post the entire design on the wiki, and anyone can lease the it for free, modify it, and manufacture their own vehicle.

But as the Fast Company blog points out, hydrogen cars may never compete with plug-in hybrids and pure electric vehicles, which is one reason why California’s “Hydrogen Highway” may be going the way of Los Angeles’s fabled streetcars.

Images of Urban Car courtesy Riversimple

*Correction (6/15/09) This sentence has been modified since the original posting.